Are You Confident of the Diagnosis?

Benign cephalic histiocytosis (BCH) is a rare non-Langerhans cell histiocytosis with spontaneous eruption of asymptomatic red to brown macules and papules. These are typically on the head but can extend to involve trunk and extremities. There is usually no mucosal, acral or visceral involvement. BCH is sometimes considered the same as neonatal acne.

Expected results of diagnostic studies

Diagnostic studies are not usually recommended, but many bedside tests may be helpful. For example, a Tzanck smear, KOH preparation or Gram stain may help rule out herpes, candidiasis, or a dermatophyte or bacterial cause. A neonatal cephalic pustulosis pustule would reveal neutrophils and rarely, eosinophils, basophils and/or lymphocytes.

Figure 2.

Immunohistochemical stains show the large mononuclear cells to be negative for CD1a. S-100 protein is usually negative or only weakly positive. By contrast, CD68 and factor XIIIa are positive. Ultrastructural studies show coated vesicles, desmosome-like structures, and worm-like or comma-shaped bodies. Birbeck granules are absent.

In JXG, lesions tend to be more widespread than in BCH and histopathology will show foamy histiocytes and Touton giant cells. LCH favors flexor surfaces and demonstrates more scaling and crusting. In addition, LCH is more likely to have associated visceral involvement and systemic symptoms such as fever and malaise. LCH shows CD1a and S100 protein positivity, and ultrastructural studies demonstrate Birbeck granules.

BCH and reticulohistiocytoma share several common features on histopathology, including an immunohistochemical staining pattern positive for CD68 and factor XIIIa, but negative for CD1a. They clinically affect different age groups (BCH in young children, reticulohistiocytoma in adults). BCH has scattered mononuclear cells, while reticulohistiocytomas contain many large mononuclear cells with ground glass cytoplasm.

Ultrastructural studies of BCH demonstrate predominantly vacuolated histiocytic cells as well as coated vesicles and desmosome-like amd worm-like bodies. By contrast, reticulohistiocytoma displays a more polymorphous pattern, both in histiocytic cell type and ultrastructural findings.

Who is at Risk for Developing this Disease?

BCH occurs mainly in young children, with an average age of onset of 15 months; 45% of cases occur in infants younger than 6 months. The incidence is equal in males and females, and BCH has been reported in a diverse range of ethnic groups. It affects approximately 10% to 20% of infants but has been reported in up to 66%. There seems to be no genetic predisposition and no known risk factors. However, Malasseszia colonization may play a role.

What is the Cause of the Disease?

Etiology

Pathophysiology

The etiology of BCH is unknown, but it is theorized to exist on a spectrum with other non-Langerhans cell histiocytoses, including generalized eruptive histiocytosis (GEH) and JXG. BCH has been suggested to be an early or aborted variant of JXG or a localized form of GEH. Two infants initially reported to have BCH on re-biopsy showed a diagnosis of JXG.

Systemic Implications and Complications

To date, there has been one report of BCH in association with diabetes insipidus and one in association with insulin-dependent diabetes mellitus. No other reports of systemic involvement have been noted and a systemic work-up is not indicated in the absence of other symptoms. In general, owing to the suggested overlap with other histiocytic disorders, regular clinical follow-up with monitoring for progression or internal involvement is recommended.

Treatment Options

BCH is usually a self-limited disorder that results in spontaneous resolution on average within 50 months. Although treatment is not usually indicated, a recent case report demonstrated accelerated regression over 3 months with use of antibiotic treatment that was required due to co-existing immmunoglobulin A deficiency and bacterial superinfection.

Optimal Therapeutic Approach for this Disease

Expectant observation and reassurance of the patient's parents until the lesions resolve are usually all that is necessary. Interval monitoring to exclude progression or internal involvement are recommended.

Patient Management

Patients and families should be counseled that the onset of resolution is expected in an average of 23 months with complete resolution occuring on average within 50 months. The eruption typically does not result in scarring but can lead to some atrophy or pigment alteration. All patients should have regular clinical follow-up to monitor for progression of cutaneous involvement as well as possible internal involvement. Owing to the self-limited nature of this disorder, conservative management is usually recommended.

Unusual Clinical Scenarios to Consider in Patient Management

Although diabetes insipidus and diabetes mellitus have been reported in patients with benign cephalic histiocytosis, such cases are rare.

(This article presents a review of 39 previously reported cases of BCH as well as summarizes demographics, duration, clinical features and course, and ultrastructural features. It compiles summary data for these cases, providing frequently used statistics on mean duration, mean age at onset, as well as clinical appearance of lesions.)

(This is the only reported case of a 5-year-old girl with BCH in association with central diabetes insipidus. This case, as well as those reported in association with diabetes mellitus, leads to the recommendation for screening in BCH for internal organ involvement and continued clinical follow-up to monitor for the development of signs or symptoms of possible internal involvement.)

(A recent case of BCH showing expression of CD11c and CD11a on the histiocytes and macrophages of the infiltrate. This case also demonstrated accelerated regression of BCH with use of antibiotics, which were necessary in this child due to IgA deficiency and bacterial superinfection.)